Next Generation Aircraft Wiring Insulation

Currently used wire harness technology consisting of Teflon-Kapton-Teflon (TKT) composite tape has significant performance issues such as hydrolysis and inadequate abrasion resistance. Engineers at V-22 primes have said one issue with kapton composite is centering – it starts to unravel and kapton becomes susceptible to hydrolysis. When pulled through conduits or been installed tape insulation edges tend to catch on even small protrusions. This can be solved with extruded insulation, but extruded insulations in the past have not met temperature requirements. A significant worry for engineers at primes is the cost of TKT composite tape and the fact that it has a single supplier – Dupont. Linden Photonics proposes the use of a new class of high temperature, high strength materials for use as extruded wire harness insulation, with the following properties: no thermal degradation up to 450 deg.C; very high tensile strength; excellent chemical stability; no hydrolysis problems even at elevated temperatures; no known arc tracking problems; extrudes well therefore low cost; Phase 1 results show that Linden’s extruded insulation passes wet arc tracking, cut through, flammability, corrosion, solvent compatibility tests as contained in the relevant SAE documents. Electrical properties, measured at AFRL, are excellent – dielectric breakdown voltage is 90 kV/mm vs. about 25 kV/mm for Teflon and kapton. High tensile strength has the potential to reduce harness weight by reducing insulation thickness. Finally extrusion is a much simpler process than tape construction and may reduce harness cost by 50%.